Outboard motor mounting arrangement



April 7, 1964 J. w. MOHR 3,127,866

OUTBOARD MOTOR MOUNTING ARRANGEMENT Filed April 27, 1962 l/l/l/I/l/l/l/ll/ l/l/l/ INVENTOR BY Jun 15 II! My:

AMAMYZWM,

United States Patent 3,127,866 OUTBOARD MOTOR MOUNTING ARRANGEMENT James W. Mohr, Brookfield, Wis., assignor to Outboard Marine Corporation, Waulregan, 111., a corporation of Delaware Filed Apr. 27, 1962, Ser. No. 190,660 20 Claims. (Cl. 115-17) The invention relates generally to outboard motors. More particularly, the invention relates to engine mounting arrangements affording sound isolation from the transom bracket.

It is known that sound isolation can be obtained by reducing the transmission of vibratory forces from a vibrating body to a supporting member by resiliently mounting the vibrating body. Transmissibility, or the rate of transmission of vibratory forces from the vibrating body to the supporting member, is a function of the ratio of the exciting vibrational frequency to the natural vibrational frequency of the supported vibrating body. Transmissibility decreases asymptotically as the ratio of exciting frequency to the natural frequency increases above the figure one (1), i.e., as the natural frequency of the vibrating body is decreased.

The invention contemplates employing these principles to obtain effective sound isolation in an outboard motor by upright, rigid mounting of a power head on the top of a strut or pedestal which is resiliently mounted at its lower end for universal angular movement relative to a supporting seat in the lower unit of a dirigible propulsion unit carried by a transom bracket.

More particularly, the natural frequency of a body which is suspended at one end varies inversely with the distance of the center of mass from the point of suspension and directly with the spring constant of the restraining force which is associated with the resilient mounting and which acts to restore the vibrating body to a neutral position of rest. Accordingly, the mounting of the relatively massive power head at the top of the strust positions the center of mass of the power head and strut assembly at a relatively long distance or radius from the universal mounting and consequently acts to decrease the natural vibrational frequency of the power head and strut assembly about the universal mounting.

In accordance with the invention, the power head is resiliently sustained centrally within the upper end of the propulsion unit and reduction of the transmisison to the propulsion unit of vibrational shaking forces and torque reaction forces is aided by spring or other resilient restoring means which connects the power head to the propulsion unit and provides restoring forces acting in opposition to the vibratory forces created by the power head. Preferably, the restoring force or forces acting in opposition to the shaking force act in a plane defined by the line of action of the shaking force and the universal mounting. In addition, the restoring force acting in opposition to torsional vibration is preferably balanced with respect to the above-mentioned plane.

The spring constant of the restoring forces should be such that, at the given distance of the center of mass from the universal mounting, there is provided a sufficiently low natural frequency of vibration which, as compared to the excitational frequency developed by the power head, will provide a sufficiently low degree of transmission to obtain effective vibrational isolation. To explain the effect in other words, the natural frequency of the power head should be capable of materially damping the exciting vibration of the power head.

In the preferred construction, the strut houses a crankshaft or drive shaft and provides a passage which connects with the both the exhaust manifold of the power 3,127,866 Patented Apr. 7, 1964 head and an exhaust passage in the lower unit, whereby exhaust gases are discharged into the water in a normal manner.

The principal object of the invention is the provision of an outboard motor having an improved vibration isolating, power head mounting arrangement. Other objects and advantages of the invention will become apparent by reference to the following description and the accompanying drawings.

FIGURE 1 is an elevational view, partially broken away and partially in section, of an outboard motor 11 embodying various of the features of the invention;

FIGURE 2 is a reduced view, partially in section, taken along line 2--2 of FIGURE 1;

FIGURE 3 is a view similar to FIGURE 2 showing another arrangement for resiliently sustaining the power head;

FIGURE 4 is a fragmentary sectional view of another arrangement embodying various of the features of the invention; and

FIGURE 5 is a fragmentary sectional view of still another arrangement embodying various of the features of the invention.

The outboard motor 11 shown in FIGURE 1 conventionally includes a transom bracket 13 adapted to be secured to the transom of a boat, a swivel bracket 15 which is hinged to the transom bracket 13 for pivotal movement about a horizontal axis or pivot 14 and a dirigible propulsion unit 17 which is pivotally supported by the swivel bracket 15 for movement about a generally upright axis or sleeve 18. The propulsion unit 17 conventionally includes a lower unit 19 housing power transmission means 21 including a drive shaft 23, a propeller shaft 25, and suitable gearing 27 connecting the driveshaft to the propeller shaft, which gearing 27 can conventionally provide for reversing the direction of rotation of the pro peller shaft by an arrangement not material to the invention. The lower unit 19 also conventionally includes an exhaust discharge passageway 29 including a discharge opening 31 which is normally submerged in water during operation and is located above and rearwardly of a propeller 33 fixed to the rearward end of the propeller shaft 25.

Unitarily connected to the upper end of the lower unit 19 is a vertically extending tubular housing 35 which is pivota-lly connected to the swivel bracket 15. Unitarily connected to the top of the tubular housing 35 is a shroud or motor cover 37 which is preferably designed to prevent or reduce the transmission of sound therefrom, as for instance, by incorporating a lining of sound absorbing material. Supported by the lower unit 19 within the propulsion unit 17 :is a power unit 40 comprising the unitary assembly of a strut or pedestal 39 and a power head or engine 41 mounted on top of the strut 39. It is preferred that the strut be hollow or tubular.

Power heads of various types can be employed. However, the disclosed sound isolating arrangement is most effective with engines which do not produce, during operation, a rocking couple such as is produced by an oppositely acting, two cylinder, internal combustion engine, i.e., the disclosed arrangement is most effective with engines such as a single cylinder engine or a V4 type engine.

The power head or engine 41 shown in the drawings conventionally includes a single cylinder 43 having operable therein a piston 45 connected by a rod 47 to a crankshaft 49. The crankshaft 49 carries a flywheel 51 and extends through the bottom of the engine block within the tubular strut 39 for connection to the driveshaft. If desired, the crankshaft can be suitably connected to an intermediate driveshaft which is journaled in the strut 3 and which, in turn, is'suitably connected to the driveshaft 23 in the lower unit 19. Preferably, the engine 41 also includes an exhaust passage 53 which discharges into the hollow strut 39. The power unit is supportingly mounted on the upper end of the lower unit by means providing for universal angular movement of the power unit 40 while supporting the weight of the unit. If desired, the supporting means can also be resilient so as to provide restoring forces acting in opposition to the vibrational forces. Various arrangements or means can be employed for supportingly mounting the power unit. In the construction shown in FIGURE 1, the power unit is carried by a ball and socket type connection including a concave seat "55 in the lower unit and the formation of the lower surface of the strut with a mating convex surface 57.

In the constructions, such as shown in FIGURE 1, where the strut 39 also serves as an exhaust tube, the concave seat 55' in the lower unit 19 is centrally opened and is in communication with the exhaust passage 29.

Other arrangements for supporting the power unit 40 includes use of an annular resilient pad or cushion 59 under the lower end '58 of the strut, such as shown in FIGURE 4. In addition, a helical coil spring 61 which is anchored at its lower end to the lower unit and received at itsupper end in telescopic arrangement with the lower end of the strut 39, as seen in FIGURE 5, can be used.

' In'the arrangement shown in FIGURE 5, it is desirable to employ a boot 63 to seal the exhaust passage 29 from the interior of the housing 35. When the arrangements shown in fFIGUR-ES 4 and are employed, the resilient characteristics of the pad 59 and spring '61 can be employed to obtain such restoring forces as will provide opposition to the shaking forces and torque reaction forces created by operation of the engine 41.

Various arrangements or means can be employed to connect or couple the crankshaft 49 to the driveshaft 23 while permitting misalignment therebetween occurring incident to vibration of the power unit 40. For instance,

' a loose splined connection can be employed. In the construction shown in FIGURE 1, the lower end of the crankshaft 49 is received in a bore 64 in the upper end of the driveshaft 2 3 and includes a pair of diametrically opposite shear pins 65 which are loosely engaged in slots 67 in the upper end of the driveshaft 23.

Other arrangements or means in addition to the before mentioned cushion 59 and coil spring 61 can be employed to resiliently stabilize the power unit 40 within the propulsion unit 17. The construction shown in FIGURE 1 includes a pair of oppositely acting coil springs 69 which are spaced from the connection between the lower end of the strut and the lower unit and are connected between the engine cover 37 of the propulsion unit 17 and the engine '41. While one of the coil springs 69-, acting both in compression and tension, can be employed to oppose the shaking force, it is preferred to employ a pair of springs which are symmetrically arranged in order to additionally oppose the vibrational torque reaction without setting up unbalanced forces acting outside of the plane defined by the shaking force and the universal mounting.

If desired, as shown in FIGURE 3, a second pair of coil springs 71 disposed at right angles to the coil springs 69 can be additionally employed so that any forces tending to dislodge the power head laterally will be resisted both in tension and in compression in the springs 71, in addition to shear resistance in the springs 69. If desired, elastomeric cushions can be employed in place of one or more of the springs 69 and 71.

Preferably, the springs 69 and 71 should be of such strength and act at such distance from the seat 55, relation to the center of mass of the power unit 40, so as to constitute the universal mounting a center of percussion, during normal operating speeds, thereby avoiding inducement of a couple requiring a horizontally'acting force at the seat 5 5 to achieve balance.

Various of the features of 'the invention are set forth in the following claims.

What is claimed is: I g 1. An outboard motor comprising a transom bracket, and a propulsion unit supported by said bracket for rotation about an upright axis, said propulsion unit comprising a lower unit including a rotatably mounted shaft carrying a propeller, the improvement comprising a power unit including a generally upright strut, and a power head rigidly mounted on the upper end of said strut, and means connecting the lower end of said strut and said lower unit for universal angular movement of said power unit relative to said lower unit. 2. An outboard motor in accordance with claim 1 wherein resilient means spaced from said means connecting said strut and said lower unit provides a second connection between said propulsion unit and said power unit.

3. An outboard motor in accordance with claim 2 wherein said resilient means is free of compression and tensile stress and is capable of extension and contraction from the normal position when said power unit is at rest. 4. An outboard motor in accordance with claim 2 wherein said power head provides a shaking force incident to operation of said power head, and

said resilient means is disposed to act in a plane defined by the line of action of said shaking force and said means connecting said strut and said lower unit.

5. An outboard motor in accordance with claim 2 wherein said resilient means comprises a pair of opposed resilient membersconnecting opposite sides of said power unit to said propulsion unit.

6. An outboard motor in accordance with claim 2 wherein said resilient means includes two pair of opposed resilient members, each of said pair of opposed members connecting opposite sides of said power unit to said propulsion unit, and one of said pair of resilient members being located transversely of the other of said pair of resilient members.

7. An outboard motor in accordance with claim 1 wherein said means connecting said strut and said lower unit'comprises a ball and socket type connection.

8. An outboard motor in accordance with claim 1 wherein said means connecting said strut and said lower unit comprises a resilient pad.

9. An outboard motor in accordance with claim 1 wherein said means connecting said strut and said lower unit comprises a coil spring.

10. An outboard motor comprising a transom bracket, and a propulsion unit supported by said bracket for rotation about an upright axis, said propulsion unit comprising a lowerunit including a rotatably mounted shaft carrying a propeller, the improvement comprising a power unit including a generally upright strut, and a power head rigidly mounted on the upper end of said strut, and

means resiliently mounting said power unit in said propulsion unit including means connecting the lower end of said strut and said lower unit for universal angular movement of said power unit relative to said lower unit.

11. An improvement in accordance with claim 19 wherein said power head includes an exhaust gas discharge port,

said lower unit includes an exhaust passage open for discharge, and

said strut is a tubular member connecting said exhaust gas discharge port and said exhaust gas passage.

12. In an outboard motor comprising a transom bracket, and a propulsion unit supported by said bracket for rotation about an upright axis, said propulsion unit comprising a lower unit including a propeller shaft carrying a propeller and a driveshaft drivingly engageable with said propeller shaft, the improvement comprising a power unit including a generally upright hollow strut, and

a power head rigidly mounted on the upper end of said strut and including a crankshaft extending in said strut,

means on said lower unit supporting the lower end of said strut for universal angular movement of said power unit relative to said lower unit, and

means for drivingly connecting said crankshaft and said driveshaft while permitting angular misalignment therebetween.

13. An outboard motor in accordance with claim 12 wherein said power head includes an exhaust gas discharge port communicating with said strut, and

said lower unit includes an exhaust passage open for discharge and communicating with said strut.

14. An outboard motor in accordance with claim 12 wherein said supporting means is resilient.

15. An outboard motor in accordance with claim 12 wherein said supporting means comprises resilient cushion means.

16. An outboard motor in accordance with claim 12 wherein resilient means spaced from said supporting means connects said propulsion unit and said power unit.

17. An outboard motor in accordance with claim 16 wherein said power head provides a shaking force incident to operation of said power head, and

said resilient means is disposed to act in a plane defined by the line of action of said shaking force and said means supporting said strut on said lower unit.

18. An outboard motor in accordance with claim 16 wherein said resilient means has a spring constant of such magnitude and is at such distance from the lower end of said strut, as to constitute said supporting means a center of percussion.

19. An outboard motor comprising a transom bracket and a propulsion unit supported by said bracket for rotation about an upright axis, said propulsion unit comprising a lower unit including a rotatably mounted shaft carrying a propeller and a drive shaft drivingly connected to said propeller shaft, a power unit including a generally upright tubular strut and a power head rigidly mounted on the upper end of said strut and including a crankshaft extending through said strut, and means resiliently mounting said power unit in said propulsion unit including means connecting the lower end of said lower unit for universal angular movement of said power unit relative to said lower unit, and flexible coupling means joining said crankshaft and said drive shaft.

20. In an outboard motor, a boat-mounted propulsion unit comprising the combination of a supporting, generally upright housing provided with driving and propeller shafts and bearings therefor and gearing connecting said shafts, and means for powering said driving shaft including a strut disposed within the supporting housing and having means for providing swiveled support for its lower end from a lower portion of the supporting housing, a power head mounted on the strut in unitary assembly therewith and thereby movable universally respecting said means for providing swiveled Support and including a power shaft having an extension projecting downwardly along the strut and provided with means for drivingly connecting it with said driving shaft, and means for yieldably positioning the power head and strut assembly in opposition to movement of the power head and strut assembly upon the means for providing swiveled support.

References Cited in the file of this patent UNITED STATES PATENTS 2,748,945 Lodge June 5, 1956 2,890,674 Rose June 16, 1959 2,909,031 Kiekhaefer Oct. 20, 1959 3,002,489 Watkins Oct. 3, 1961 

1. AN OUTBOARD MOTOR COMPRISING A TRANSOM BRACKET, AND A PROPULSION UNIT SUPPORTED BY SAID BRACKET FOR ROTATION ABOUT AN UPRIGHT AXIS SAID PROPULSION UNIT COMPRISING A LOWER UNIT INCLUDING A ROTATABLY MOUNTED SHAFT CARRYING A PROPELLER; THE IMPROVEMENT COMPRISING A POWER UNIT INCLUDING A GENERALLY UPRIGHT STRUT, AND A POWER HEAD RIGIDLY MOUNTED ON THE UPPER END OF SAID STRUT, AND MEANS CONNECTING THE LOWER END OF SAID STRUT AND SAID LOWER UNIT FOR UNIVERSAL ANGULAR MOVEMENT OF SAID POWER UNIT RELATIVE TO SAID LOWER UNIT. 